OpAssign in macros doesn't work for container types

[Blacksmoke16]

#9409 made it so OpAssign are supported in macro land. However it doesn't seem to work when using it with a container type, like HashLiteral or NamedTupleLiteral:

{% begin %}
  {% hash = {} of Nil => Nil %}
  
  {% pp(hash["foo"] ||= {"id" => 1}) %}
{% end %}

Produces: Error: undefined macro method 'HashLiteral#[]?'.

This seems to be because, unlike the related stdlib types, the macro variants do not have a #[]? method as they rely solely on #[]. Either need to have the op assign logic account for that, or could just add #[]? as an undocumented alias on the macro types.

Discovered via athena-framework/athena#151.